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Gets configuration variable for path name. Syntax | |
#include <unistd.h>
long pathconf(char *pathname, int name);
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Parameters | |
- pathname
is the name of the file or directory.
- name
is a symbol indicating the variable, the value of which
you want to determine, relative to the file or
directory specified in pathname. .
Description | |
pathconf() lets you determine the value of a configuration
variable associated with a particular file. If pathconf()
can determine the value of the requested variable, it
returns that value as its result. The name argument may be any one of a set of symbols
defined in <unistd.h>. Each symbol stands for a
configuration variable. The following list shows the
possible symbols and the variables that each symbol stands for: - _PC_LINK_MAX
stands for LINK_MAX defined in <limits.h> -- the
maximum number of links the file can have. If pathname
is a directory, pathconf() returns the maximum number
of links which can be established to the directory
itself.
- _PC_MAX_CANON
stands for MAX_CANON defined in <limits.h> -- the
maximum number of bytes in a terminal canonical input
line. pathname must refer to a terminal file.
- _PC_MAX_INPUT
stands for MAX_INPUT defined in <limits.h> -- the
minimum number of bytes for which space is available in
a terminal input queue, which means the maximum number
of bytes that a portable application may have the user
enter before the application actually reads the input.
pathname must refer to a terminal file.
- _PC_NAME_MAX
stands for NAME_MAX defined in <limits.h> -- the
maximum number of characters in a filename (not
including any terminating 0 if the filename is stored
as a string). This only refers to the filename
itself, that is, the last component of the file's path
name. pathname must be a directory, and pathconf()
returns the maximum length of filenames for files in
the directory.
- _PC_PATH_MAX
stands for PATH_MAX defined in <limits.h> -- the
maximum number of characters in a complete path name (not including any terminating \0 if the path name is stored as a string). pathname must be a directory, and
pathconf() returns the maximum length of a relative
path name when the specified directory is the working directory.
- _PC_PIPE_BUF
stands for PIPE_BUF defined in <limits.h> -- the
maximum number of bytes that can be written
`atomically' to a pipe. If more than this number of
bytes are written to a pipe, the operation may take
more than one physical write operation and may require
more than one physical read operation to read the data
on the other end of the pipe. If pathname is a FIFO
file, pathconf() returns the value for the file itself.
If pathname is a directory, pathconf() returns the
value for any FIFOs which exist or can be created under
the directory. If pathname is any other kind of file,
the behavior is undefined.
- _PC_CHOWN_RESTRICTED
stands for _POSIX_CHOWN_RESTRICTED defined in the <unistd.h>.
This indicates that the use of the chown()
function is restricted -- see chown() for more
details. If pathname is a directory, pathconf()
returns the value for any kind of file under the
directory, but not for subdirectories of the directory.
- _PC_NO_TRUNC
stands for _POSIX_NO_TRUNC defined in <unistd.h>. This
indicates that an error is to be generated if a file
name is longer than NAME_MAX. pathname must be a
directory, and the value returned by pathconf() applies
to all files under that directory.
- _PC_VDISABLE
stands for _POSIX_VDISABLE defined in <unistd.h>. This indicates that terminal special characters can be disabled using this character value, if it is defined; see tcsetattr() for details. pathname must refer to a terminal file.
For _POSIX_CHOWN_RESTRICTED, _POSIX_NO_TRUNC, and
_POSIX_VDISABLE, pathconf() returns -1 if the option is
turned off and another value otherwise. If a particular variable has no limit (for example
PATH_MAX), pathconf() returns -1 but does not change
errno. Errors | |
If pathconf() cannot determine an appropriate value, it returns -1 and sets errno to one of the following: | EACCES | CAUSE
| The process does not have search permission on
some component of the pathname prefix. | | | ACTION
| Ensure that the process has search permissions on
all components of the pathname prefix.
| | EINVAL | CAUSE
| name is not a valid variable code, or the given
variable cannot be associated with the specified
file. | | | ACTION
| Ensure that name is a valid variable code.
| | ENAMETOOLONG | CAUSE
| pathname is longer than PATH_MAX characters, or
some component of pathname is longer than NAME_MAX
and _POSIX_NO_TRUNC is set. | | | ACTION
| Unset the configuration variable _POSIX_NO_TRUNC'
to disable checking the length of pathname or
modify pathname to ensure that the entire name is
less than ``PATH_MAX characters in length and that
each component is less than NAME_MAX characters in
length.
| | ENOENT | CAUSE
| There is no filenamed pathname, or the pathname
argument is an empty string. | | | ACTION
| Ensure that you provide a pathname and that
pathname is a valid file.
| | ENOTDIR | CAUSE
| Some component of the pathname prefix is not a
directory. | | | ACTION
| Ensure that all components of pathname are valid
directories.
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See Also | |
fpathconf() |
